In these years, liquid crystal display devices are in widespread use as displays for household electrical appliances such as computers and television receiving devices. A general liquid crystal display device includes a liquid crystal display panel, and an illuminating device that is disposed behind the display panel so as to project light onto the display panel. A side-light (or edge-light) type illuminating device that includes a light guide plate, and a light source that is disposed along one side or a plurality of sides of the light guide plate is known as this type of illuminating device. The side-light illuminating device having this configuration has the advantage of being easily reduced in thickness, compared with a direct illuminating device having a configuration that a light source is disposed behind a liquid crystal display panel.
A general light guide plate is a transparent plate having a given thickness, which is made from an acrylate resin. The general light guide plate planarly diffuses light from a light source, which has entered from its lateral end face (light entrance face), on its front face (light exit face). The light guide plate needs to be positioned or fixed in a box-shaped chassis included in an illuminating device so as not to be displaced or not to fall off. However, a mechanism or a structure to position or fix the light guide plate in the chassis should not cause nonuniform in-plane intensity distribution of the light emitted from the front face of the light guide plate. For example, PTL 1 discloses a configuration to fix a light guide plate in a chassis.
Disclosed in PTL 1 is the configuration that the light guide plate includes a through hole or a notch in a plate thickness direction on its outer peripheral end portion, and that a chassis that houses the light guide plate includes a protrusion or a column. The through hole or the notch of the light guide plate engages with the protrusion or the column of the chassis, whereby the light guide plate is positioned or fixed in the chassis.